Organosilicon compounds, making methods, and adhesion improver

ABSTRACT

Mercapto-containing organosilicon compounds of specific structure are low volatile and serve to enhance the adhesion of resins to inorganic substrates.

CROSS-REFERENCE TO RELATED APPLICATION

This non-provisional application claims priority under 35 U.S.C. §119(a)on Patent Application No. 2013-123638 filed to in Japan on Jun. 12,2013, the entire contents of which are hereby incorporated by reference.

TECHNICAL FIELD

This invention relates to novel organosilicon compounds, methods forpreparing the same, and an adhesion improver comprising the same as anactive ingredient.

BACKGROUND ART

Mercapto-containing organosilicon compounds are widely used as adhesionimprovers for resins to inorganic substrates such as glass and metalmaterials. As described in JP 4692885, for example, mercapto-containingorganosilicon compounds are added to epoxy resins for the purpose ofimproving the adhesion of the epoxy resin to a leadframe. Of themercapto-containing organosilicon compounds,3-mercaptopropyltrimethoxysilane and3-mercaptopropylmethyldimethoxysilane are commonly used.

Since these mercapto-containing organosilicon compounds have low boilingpoints, they will volatilize off during high-temperature coating. Thusthe mercapto-containing organosilicon compounds must be added more thanthe necessity. In addition, the surrounding equipment can becontaminated with the volatilizing compounds.

CITATION LIST

Patent Document 1: JP 4692885 (WO 2004/074344)

DISCLOSURE OF INVENTION

An object of the invention is to provide a mercapto-containingorganosilicon compound which is low volatile and has high adhesion toinorganic substrates, a method for preparing the same, and an adhesionimprover comprising the same.

The inventor has found that mercapto-containing organosilicon compoundshaving the general formulae (1) to (3) are low volatile and have highadhesion to inorganic substrates.

The invention provides organosilicon compounds, methods for preparingthe same, and an adhesion improver, defined below.

-   [1] An organosilicon compound having the general formula (1):

wherein A is independently a straight or branched C₁-C₈ alkylene group,B is independently a straight or branched C₁-C₈ alkylene group, D isindependently a straight or branched C₁-C₈ alkylene group, R isindependently a hydrolyzable group, R′ is independently a C₁-C₄ alkylgroup, a is a number of 1 to 4, b is a number of 0 to 3, c is 0 or 1,a+b+c is 4, and m is an integer of 1 to 3.

-   [2] An organosilicon compound having the general formula (2):

wherein A is independently a straight or branched C₁-C₈ alkylene group.B is independently a straight or branched C₁-C₈ alkylene group, D isindependently a straight or branched C₁-C₈ alkylene group, R isindependently a hydrolyzable group, R′ is independently a C₁-C₄ alkylgroup, m is an integer of 1 to 3, a′ is a number of 0 to 3, b′ is anumber of 0 to 3, c′ is 0 or 1, a′+b′+c′ is 3, a″ is a number of 0 to 3,b″ is a number of 0 to 3, c″ is 0 or 1, a″+b′+c″ is 3, and a′+a″ is anumber of 1 to 6.

-   [3] An organosilicon compound having the general formula (3):

wherein A is independently a straight or branched C₁-C₈ alkylene group.B is independently a straight or branched C₁-C₈ alkylene group, E isindependently hydrogen or a substituent group of the general formula(4):

wherein D is independently a straight or branched C₁-C₈ alkylene group,R is independently a hydrolyzable group, R′ is independently a C₁-C₄alkyl group, and m is an integer of 1 to 3, at least one E being asubstituent group of formula (4).

-   [4] The organosilicon compound of [1], having the general formula    (5):

wherein R, R′, m, a, b, c, and a+b+c are as defined above.

-   [5] The organosilicon compound of [2], having the general formula    (6):

wherein R, R′, m, a′, b′, c′, a′+b′+c′, a″, b″, c′, a″+b″+c″, and a′+a″are as defined above.

-   [6] The organosilicon compound of [3], having the general formula    (7):

wherein E is as defined above.

-   [7]A method for preparing the organosilicon compound of [1],    comprising the step of reacting a mercapto compound having the    general formula (8):

wherein A and B are as defined above, d is 3 or 4, e is 0 or 1, d+e is4, with an isocyanate-containing organosilicon compound having thegeneral formula (a):

wherein D, R, R′, and m are as defined above.

-   [8]A method for preparing the organosilicon compound of [2],    comprising the step of reacting a mercapto compound having the    general formula (9):

wherein A and B are as defined above, f is 3 or 4, g is 0 or 1, f+g is4, f′ is 3 or 4, g′ is 0 or 1, f′+g′ is 4, with an isocyanate-containingorganosilicon compound having the general formula (a):

wherein D, R, R′, and m are as defined above.

-   [9]A method for preparing the organosilicon compound of [3],    comprising the step of reacting a mercapto compound having the    general formula (10):

wherein A and B are as defined above, with an isocyanate-containingorganosilicon compound having the general formula (a):

wherein D, R, R′, and m are as defined above.

-   [10] The method of any one of [7] to [9] wherein the    isocyanate-containing organosilicon compound is    3-isocyanatopropyltrimethoxysilane,    3-isocyanatopropylmethyldimethoxysilane,    3-isocyanatopropyltriethoxysilane, or    3-isocyanatopropylmethyldiethoxysilane.-   [11] An adhesion improver for improving adhesion to inorganic    substrates, comprising the organosilicon compound of any one of [1]    to [6] as an active ingredient.

Advantageous Effects of Invention

Since the organosilicon compound of the invention has (1) a hydrolyzablesilyl group, (2) a thiourethane structure, and (3) a mercapto group in amolecule, it can afford high adhesion to inorganic substrates. Since theorganosilicon compound is low volatile, it causes least contamination tothe surrounding equipment when used as the adhesion improver. Animprovement in productivity is expectable therefrom. An economicaladvantage is obtained in that an improvement in adhesion is achievablewith a necessary minimum amount of the compound.

DESCRIPTION OF EMBODIMENTS

Throughout the specification, Me stands for methyl. The notation “Cn-Cm”means a group containing from n to m carbon atoms per group. Herein, the“silane coupling agent” is encompassed in the “organosilicon compound.”

Organosilicon Compound

One embodiment of the invention is directed to organosilicon compoundshaving the general formulae (1), (2), and (3).

Herein A is independently a straight or branched C₁-C₈ alkylene group, Bis independently a straight or branched C₁-C₈ alkylene group, D isindependently a straight or branched C₁-C₈ alkylene group, R isindependently a hydrolyzable group, R′ is independently a C₁-C₈ alkylgroup, a is a number of 1 to 4, b is a number of 0 to 3, c is 0 or 1,a+b+c is 4, and m is an integer of 1 to 3.

Herein A, B, D, R, R′ and m are as defined above, a′ is a number of 0 to3, b′ is a number of 0 to 3, c′ is 0 or 1, a′+b′+c′ is 3, a″ is a numberof 0 to 3, b″ is a number of 0 to 3, c″ is 0 or 1, a″+b″+c″ is 3, anda′+a″ is a number of 1 to 6.

Herein A and B are as defined above, E is independently hydrogen or asubstituent group of the general formula (4):

wherein D, R, R′, and m are as defined above, at least one E being asubstituent group of formula (4).

Specifically, suitable straight or branched C₁-C₈ alkylene groupsrepresented by A include CH₂, C₂H₄, C₃H₆, C₄H₈, C₅H₁₀, C₆H₁₂, C₇H₁₄, andC₈H₁₆. Suitable straight or branched C₁-C₈ alkylene groups representedby B include CH₂, C₂H₄, C₃H₆, C₄H₈, C₅H₁₀, C₆H₁₂, C₇H₁₄, and C₈H₁₆.Suitable straight or branched C₁-C₈ alkylene groups represented by Dinclude CH₂, C₂H₄, C₃H₆, C₄H₈, C₅H₁₀, C₆H₁₂, C₇H₁₄, and C₈H₁₆. It ispreferred for availability of starting reactants that A be C₂H₄, B beC₂H₄, and D be C₃H₆. Suitable hydrolyzable groups represented by Rinclude halogen atoms such as chlorine and bromine, and alkoxy groupssuch as methoxy and ethoxy. Of these, alkoxy groups are preferred, withmethoxy being most preferred. Suitable C₁-C₈ alkyl groups represented byR′ include methyl, ethyl, and propyl, with methyl being preferred.

The subscript m is an integer of 1 to 3, preferably 3, a is a number of1 to 4, preferably 1 to 2, b is a number of 0 to 3, preferably 2 to 3, cis 0 or 1, and a+b+c is equal to 4. The subscript a′ is a number of 0 to3, preferably 1 to 2, b′ is a number of 0 to 3, preferably 2 to 3, c′ is0 or 1, a′+b′+c′ is equal to 3, a″ is a number of 0 to 3, preferably 1to 2, b″ is a number of 0 to 3, preferably 2 to 3, c″ is 0 or 1,a″+b″+c″ is equal to 3, and a′+a″ is a number of 1 to 6, preferably 1 to3.

The preferred organosilicon compound of formula (1) has the generalformula (5):

wherein R, R′, m, a, b, c, and a+b+c are as defined above.

The preferred organosilicon compound of formula (2) has the generalformula (6):

wherein R, R′, m, a′, b′, c′, a′+b′+c′, a″, b″, c″, a″+b″+c″, and a′+a″are as defined above.

The preferred organosilicon compound of formula (3) has the generalformula (7):

wherein E is as defined above.

Exemplary structures of the organosilicon compound of formula (1) areshown below, but not limited thereto.

An exemplary structure of the organosilicon compound of formula (2) isshown below, but not limited thereto.

An exemplary structure of the organosilicon compound of formula (3) isshown below, but not limited thereto.

Method

Another embodiment of the invention is directed to methods for preparingthe organosilicon compounds of formulae (1) to (3). The organosiliconcompound of formula (1) is prepared by reacting a mercapto compoundhaving the general formula (8):

wherein A and B are as defined above, d is 3 or 4, e is 0 or 1, d+e is4, with an isocyanate-containing organosilicon compound having thegeneral formula (a):

wherein D, R, R′, and m are as defined above.

Examples of the mercapto compound of formula (8) includetrimethylolpropane tris(3-mercaptopropionate) and pentaerythritoltetrakis(3-mercaptopropionate), but are not limited thereto.

Examples of the isocyanate-containing organosilicon compound of formula(a) include, but are not limited to, 3-isocyanatopropyltrimethoxysilane,3-isocyanatopropylmethyldimethoxysilane,3-isocyanatopropyltriethoxysilane, and3-isocyanatopropylmethyldiethoxysilane.

Of these, 3-isocyanatopropyitrimethoxysilane and3-isocyanatopropyltriethoxysilane are preferred for availability ofstarting reactant.

In the reaction of the mercapto compound of formula (8) with theisocyanate-containing organosilicon compound of formula (a), it ispreferred to use 1 to 3 moles, especially 1 to 2 moles of theorganosilicon compound per mole of the mercapto compound.

Also, the organosilicon compound of formula (2) is prepared by reactinga mercapto compound having the general formula (9):

wherein A and B are as defined above, f is 3 or 4, g is 0 or 1, f+g is4, f′ is 3 or 4, g′ is 0 or 1, f′+g′ is 4, with an isocyanate-containingorganosilicon compound having the general formula (a):

wherein D, R, R′, and m are as defined above.

Exemplary of the mercapto compound of formula (9) is dipentaerythritolhexakis(3-mercaptopropionate). Examples of the isocyanate-containingorganosilicon compound of formula (a) are as illustrated above, but notlimited thereto.

In the reaction of the mercapto compound of formula (9) with theisocyanate-containing organosilicon compound of formula (a), it ispreferred to use 1 to 6 moles, especially 1 to 2 moles of theorganosilicon compound per mole of the mercapto compound.

Further, the organosilicon compound of formula (3) is prepared byreacting a mercapto compound having the general formula (10):

wherein A and B are as defined above, with an isocyanate-containingorganosilicon compound having the general formula (a):

wherein D, R, R′, and m are as defined above.

Exemplary of the mercapto compound of formula (10) istris[(3-mercaptopropionyloxy)ethyl]isocyanurate. Examples of theisocyanate-containing organosilicon compound of formula (a) are asillustrated above, but not limited thereto.

In the reaction of the mercapto compound of formula (10) with theisocyanate-containing organosilicon compound of formula (a), it ispreferred to use 1 to 3 moles, especially 1 to 2 moles of theorganosilicon compound per mole of the mercapto compound.

As illustrated above, the organosilicon compounds of the invention maybe prepared by reaction of a polyfunctional mercapto compound with anorganosilicon compound having an isocyanate group. A plurality ofreaction sites are involved in the reaction. In an example where atetra-substituted mercapto compound is reacted with an organosiliconcompound having an isocyanate group, there is produced a mixture ofzero, mono, di, tri and tetra-substituted compounds, as shown by thegeneral formula (15).

Herein, Y is a residue of the polyfunctional mercapto compound, and Z isa residue of the isocyanate-containing organosilicon compound.

Since the organosilicon compound of the invention is available as amixture of a plurality of compounds as indicated above, the foregoingformulae (1) to (14) each represent an average composition. Therefore,even when the reaction product is a mono-substituted compound as theaverage composition, otherwise substituted compounds are in admixturetherewith.

In preparing the organosilicon compound, a solvent may be used ifnecessary. The solvent used herein is not particularly limited as longas it is inert to the reactants, mercapto compound andisocyanate-containing organosilicon compound. Suitable solvents includealiphatic hydrocarbon solvents such as pentane, hexane, heptane anddecane, ether solvents such as diethyl ether, tetrahydrofuran, and1,4-dioxane, amide solvents such as formamide, dimethylformamide, andN-methylpyrrolidone, and aromatic hydrocarbon solvents such as benzene,toluene, and xylene.

In preparing the organosilicon compound, a catalyst may be used ifnecessary. Although the catalyst used herein may be any of the catalystscommonly used in isocyanate reaction, tin compounds and amine catalystsare preferred. As the tin catalyst, salts of tin(II) with carboxylicacids such as dioctyltin oxide are preferred for catalytic activity.Preferred amine catalysts are tertiary amines such as triethylamine,tributylamine and N-ethyldiisopropylamine. Preferably the catalyst maybe used in an amount of 0.0000001 to 1 mole, more preferably 0.000001 to0.01 mole per mole of the isocyanate-containing organosilicon compound.More than 1 mole of the catalyst may be uneconomical because thecatalytic effect is saturated. Less than 0.0000001 mole of the catalystmay lead to a short catalytic effect, a low reaction rate, and lowproductivity.

In preparing the organosilicon compound, the reaction is exothermic.Side reactions may occur at unnecessarily high temperatures. Therefore,the reaction temperature is preferably controlled to a range of 20 to150° C. more preferably 30 to 130° C., and even more preferably 40 to110° C. Temperatures below 20° C. may lead to a low reaction rate andlow productivity. At temperatures above 150° C. side reactions,typically polymerization reaction of the isocyanate-containingorganosilicon compound may take place.

The reaction time required until the organosilicon compound is obtainedis not particularly limited as long as the temperature control ispossible despite exothermic reaction and exothermic reaction iscompleted within the time. Preferably the reaction time is 10 minutes to24 hours, more preferably 1 to 10 hours.

The organosilicon compound of the invention finds use as an adhesionimprover to inorganic substrates such as glass and metal materials.Conventional mercapto-containing organosilicon compounds are adherent toinorganic substrates such as glass and metal materials. Since theorganosilicon compound of the invention has a plurality of mercaptogroups per hydrolyzable group and a urethane bond and ester bond as thepolar group, it is expected to exhibit higher adhesion than theconventional mercapto-containing organosilicon compounds when added toepoxy, urethane, acrylic and polyimide resins in an amount of 0.1 to 20%by weight.

EXAMPLE

Examples of the invention are given below by way of illustration and notby way of limitation. In Examples, Me stands for methyl, and IR forinfrared.

Example 1

Preparation of Organosilicon Compound (11)

A 1-L separable flask equipped with a stirrer, reflux condenser,dropping funnel and thermometer was charged with 399 g (1 mol) oftrimethylolpropane tris(3-mercapto-propionate) (TMMP by Sakai ChemicalIndustry Co., Ltd.) and 0.06 g of dioctyltin oxide and heated at 80° C.To the flask, 205 g (1 mol) of 3-isocyanatopropyltrimethoxysilane wasadded dropwise, followed by 2 hours of stirring at 80° C. The reactionwas terminated when the complete extinction of absorption peaks assignedto the isocyanate group in the reactant was confirmed by IRspectrometry. On purification by filtration, the product was a colorlessclear liquid. The mercapto equivalent was measured to be 303, which wassubstantially equal to the theoretical value of 301. This organosiliconcompound is designated Silane A.

Example 2

Preparation of Organosilicon Compound (12)

A 1-L separable flask equipped with a stirrer, reflux condenser,dropping funnel and thermometer was charged with 489 g (1 mol) ofpentaerythrytol tetrakis(3-mercapto-propionate) (PEMP by Sakai ChemicalIndustry Co., Ltd.) and 0.06 g of dioctyltin oxide and heated at 80° C.To the flask, 205 g (1 mol) of 3-isocyanatopropyltrimethoxysilane wasadded dropwise, followed by 2 hours of stirring at 80° C. The reactionwas terminated when the complete extinction of absorption peaks assignedto the isocyanate group in the reactant was confirmed by IRspectrometry. The product was a colorless clear liquid. The mercaptoequivalent was measured to be 233, which was substantially equal to thetheoretical value of 231. This organosilicon compound is designatedSilane B.

Example 3

Preparation of organosilicon compound (13) A 2-L separable flaskequipped with a stirrer, reflux condenser, dropping funnel andthermometer was charged with 783 g (1 mol) of dipentaerythrytolhexakis(3-morcapto-propionate) (DPMP by Sakai Chemical Industry Co.,Ltd.) and 0.06 g of dioctyltin oxide and heated at 80° C. To the flask,205 g (1 mol) of 3-isocyanatopropyltrimethoxysilane was added dropwise,followed by 2 hours of stirring at 80° C. The reaction was terminatedwhen the complete extinction of absorption peaks assigned to theisocyanate group in the reactant was confirmed by IR spectrometry. Theproduct was a colorless clear liquid. The mercapto equivalent wasmeasured to be 201, which was substantially equal to the theoreticalvalue of 197. This organosilicon compound is designated Silane C.

Example 4

Preparation of Organosilicon Compound (14)

A 1-L separable flask equipped with a stirrer, reflux condenser,dropping funnel and thermometer was charged with 526 g (1 mol) oftris[(3-mercaptopropionyloxy)ethyl]isocyanurate (TEMPIC by SakaiChemical Industry Co., Ltd.) and 0.06 g of dioctyltin oxide and heatedat 80° C. To the flask, 205 g (1 mol) of3-isocyanatopropyltrimethoxysilane was added dropwise, followed by 2hours of stirring at 80° C. The reaction was terminated when thecomplete extinction of absorption peaks assigned to the isocyanate groupin the reactant was confirmed by IR spectrometry. The product was acolorless clear liquid. The mercapto equivalent was measured to be 370,which was substantially equal to the theoretical value of 365. Thisorganosilicon compound is designated Silane D.

Example 5 and Comparative Example 1

Volatility of Organosilicon Compounds

The organosilicon compounds (11) to (14) obtained above, that is,Silanes A to D and Silane E (described below) were evaluated forvolatility. In the test, 1 g of the compound was dropped on an aluminumdish, which was allowed to stand in an open constant-temperature chamberat 105° C. for 3 hours, after which the residue was evaluated as thenonvolatile content. A greater nonvolatile content indicates lowervolatility. The results are shown in Table 1.

-   Silane E: 3-mercaptopropyltrimethoxysilane (KBM-803 by Shin-Etsu    Chemical Co., Ltd.)

TABLE 1 Compound Nonvolatile content (%) Example 5 Silane A 98 Silane B99 Silane C 99 Silane D 99 Comparative Example 1 Silane E 0

As seen from the data, the organosilicon compounds within the scope ofthe invention are least volatile. Thus the volatilization of thecompound during high-temperature application is fully suppressed. Thecompound exerts its desired effect when added in a necessary minimumamount, with an economical advantage. In addition, contamination of thesurrounding equipment is suppressed, and an improvement in productivityis expectable.

Examples 6 to 9 and Comparative Examples 2 to 4

Adhesion of organosilicon compounds

An epoxy resin composition to which the organosilicon compound was addedwas evaluated for adhesion. Specifically, the epoxy resin compositionconsisted of an epoxy resin YDPN638 (Nippon Steel & Sumikin ChemicalCo., Ltd.), 2-methylimidazole as a catalyst, and Silane A, B, C, D or E(identified above). The composition was applied onto a glass plate to acoating thickness of 10 μm by means of a bar coater, cured at 150° C.for 1 hour, and examined by a cross-hatch adhesion test according to JISK-5400. The formulation (in parts by weight) of the composition is shownin Table 2 together with the test results.

TABLE 2 Formulation (pbw) Example Comparative Example 6 7 8 9 2 3 4Epoxy resin 98 98 98 98 98 98 98 Catalyst 2 2 2 2 2 2 2 Silane A 0.5Silane B 0.5 Silane C 0.5 Silane D 0.5 Silane E 2.0 0.5 Test resultsAdhesion 100/ 100/ 100/ 100/ 90/ 70/ 50/ 100 100 100 100 100 100 100

As seen from the test results, the organosilicon compounds within thescope of the invention are effective for improving the adhesion of epoxyresin compositions to glass substrates even in a minimal amount ofaddition.

Japanese Patent Application No. 2013-123638 is incorporated herein byreference.

Although some preferred embodiments have been described, manymodifications and variations may be made thereto in light of the aboveteachings. It is therefore to be understood that the invention may bepracticed otherwise than as specifically described without departingfrom the scope of the appended claims.

The invention claimed is:
 1. An organosilicon compound having theformula(1):

wherein A is independently a straight or branched C₁-C₈ alkylene group,B is independently a straight or branched C₁-C₈ alkylene group, D isindependently a straight or branched C₁-C₈ alkylene group, R isindependently a hydrolyzable group selected from the group consisting ofhalogen atoms and alkoxy groups, R′ is independently a C₁-C₄ alkylgroup, a is a number of 1 to 4, b is 2, c is 0 or 1, a+b+c is 4, and mis an integer of 1 to
 3. 2. The organosilicon compound of claim 1,having the formula (5):

wherein R, R′, m, a, b, c, and a+b+c are as defined in claim
 1. 3. Amethod for preparing the organosilicon compound of claim 1, comprisingthe step of reacting a mercapto compound having the formula (8):

wherein A and B are as defined in claim 1, d is 3 or 4, e is 0 or 1, d+eis 4, with an isocyanate-containing organosilicon compound having theformula (a):

wherein D, R, R′, and m are as defined in claim
 1. 4. The method ofclaim 3 wherein the isocyanate-containing organosilicon compound is3-isocyanatopropyltrimethoxysilane,3-isocyanatopropylmethyldimethoxysilane,3-isocyanatopropyltriethoxysilane, or3-isocyanatopropylmethyldiethoxysilane.
 5. A resin composition havingimproved adhesion to inorganic substrates, comprising: 0.1 to 20weight-% of the organosilicon compound of claim 1 as an activeingredient; and a resin selected from the group consisting of epoxyresins, urethane resins, acrylic resins, and polyimide resins.
 6. Aresin composition having improved adhesion to inorganic substrates,comprising: 0.1 to 20 weight-% of the organosilicon compound of claim 2as an active ingredient; and a resin selected from the group consistingof epoxy resins, urethane resins, acrylic resins, and polyimide resins.